Initiator manufacturing apparatus



Feb. 23, 1954 c. R. JOHNSON 2,670,465

INITIATOR MANUFACTURING APPARATUS Filed May 21, 1952 3 Sheets-Sheet l INVENTOR.

' 4 CHARLES RUSSELL JOHNSON UUUUUUUUUH A TTORNE Y S.

Feb. 23, 1954 c. R. JOHNSON ,670,4

INITIATOR MANUFACTURING APPARATUS Filed May 21, 1952 3 Sheets-Sheet 2 inw IN V EN TOR. CH ABLE 5 R USSELL JOHNSON BY Wm. 4 m

ATTORNEYS.

Feb. 23, 1954 v c. R. JOHNSON 2 ,670,465

INIT IATOR MANUFACTURING APPARATUS Filed May 21, 1952 3 Sheets-Sheet 3 2? I 5| f T 4. H b -u c v u- DETECTOR b 30 CIRCUIT Il LOWERING go CIRCUIT RAISING ClRCUIT v Ll 34 F START AND STOP ClRCUlT MOTOR CIRCUIT C I T WARNING J CIRCUIT 2, 33

I.\'\ENT()R CHARLES-RUSSELL JOHNSON 7 I A 544/. Q/fim BY %4 Y Patented Feb. 23, 1954 INITIATOR MANUFACTURING APPARATUS Charles Russell Johnson, Glen Pa., as-- signor to E. I. du Pont de Nemours and Company, Wilmington, Del., a corporation of Delaware Application May 21,1952, Serial No. 289,023

3 Claims. 1

The present invention relates to a machine for use in the manufacture of blasting initiators. More particularly, this invention relates to a probing device adapted to check the initiator shells for proper loading of the explosive charges.

Blasting initiators generally are manufactured by loading a sensitive explosive charge capable of detonating a blasting explosive into a metal shell, and providing an ignition charge in association with this charge, the ignition charge being adapted to become ignited by the action of a fuse or a heated bridge wire and to initiate the main or base charge. In the case of electric initiators, the installation of the bridge wire assembly is a final step in the manufacture of the initiator, while in the case of a fuse-ignitable initiator, the pressing of the last charge completes the fabrication operation. In many types of initiators, more than two charges of explosive material are used, and, in some cases, the final charge consists of a loose powder into which a bridge Wire is inserted. In practically all cases, the main charge and the charge adapted to ignite the main charge are compacted by a pressing operation during the assembly of the initiator.

Since blasting initiators of various types are mass produced by means of automatic fabricating and loading machines, it is essential that accurate and efficient means be provided to insure against defective initiators. Due to the nature of the explosive compositions used in initiators, it is desirable to reduce the handling of the uncompleted initiators by personnel to a minimum, not only from a safety viewpoint, but also to eliminate human error.

One major cause of defective blasting initiators has been uneven loading of the pressed charges. By far the greater number of initiators produced annually are loaded by automatic loading devices, and, while these devices are efiicient and accurate in controlling the quantity of explosive inserted into a shell, it sometimes happens that an insufficient quantity of explosive material is present in the loading machine, or that one or more of the loading ports becomes closed or inoperative, thereby producing an initiator without any charge or an inadequate charge.

It is an object of the present invention to provide a completely automatic initiator charge checking device. A further object of the present invention is to provide a device for rapidly and accurately inspecting partially assembled initiator charges. Additional objects will become apparent as the invention is more fully described. I have found that the foregoing objects may be attained when I provide an initiator probingdevice having a plurality of individual probes adapted to be entered into a block of initiator shells, said probes being held in an extended posiis made to the accompanying drawings which illustrate a specific embodiment, it being understood that the invention is not limited thereto. In the drawings:

Figure 1 represents a partially sectional frontal view;

Figure 2 represents a partially sectional side view;

Figures 3, 4 and 5 represent a detail viewof the probe action and detecting means;

Figure 6 represents a detail view of the indicator'operation; and

Figure '7 shows a suitable signal and control circuit.

Referring to the figures in greater detail, I represents the structural support for the apparatus, 2 represents a shaft connecting the probing assembly with motive means (not shown) for lowering and raising the assembly, 3 is the housing of the probing assembly mounted on base plate 4 and suspended on shaft 2. Within the housing 3 are the probing elements 5 and the detecting plate 6. The probing elements 5 contain an enlarged portion and are positioned by means of bores l in the housing 3, and guide bushings 8 in base plate 4, and held normally extended by coil springs 9. element 5 is an initiator shell I!) supported and positioned by conventional means (not shown). Between the shells l0 and the base plate 4 is the shell locking plate ll suspended on bolts l2. Each bolt l2 has a projecting arm l3 secured to the upper end, and passes through a support member l4 mounted on base plate 4. The plate H is maintained in an extended position by coil :return disc I8 is mounted on shaft 19 which in Directly beneath each probing turn is connected to a mechanical means (not shown) for applying and removing pressure to roller 11. Mounted on housing a above the de tector plate 6 is microswitch 24 aligned with pin 23 on plate 6.

Mounted on support I on each side under arm 43 are the shell-locking plate It and stops 2!]. These stops are positioned below arm [3 a distance equal to the normal distance between the tops of the shells and the bottom of the shelllocking plat H, and are adjustable so that the device may be used with different length shells.

In Figures 3, 4 and 5, the initiator shells are represented as containing base charge 2| and a priming charge 22. The probe 5 is designed as to contact only the priming charge 22 or in its absence, to enter the depression in charge 2] it would otherwise occupy. It will be understood that the depression in the base charge 2| would be produced by the first pressing operation.

In operation, the procedure is as follows:

A block of initiator shells H) from the loadin machine is positioned under the probing assembly, either by mechanical or manual means, and the housing 3 lowered by lowering shaft 2. Plate H descends with housing 3 until the arms 13 contact the stops 2t. At this time, plate H is just touching the tops of the shells, thus insuring that all shells are properly seated and upright. The continued downward movement of shaft 2 causes the probing elements 5 to enter the shells, and compresses springs l5, bolts l2 being prevented from further downward movement.

During the downward movement of housing 3, mechanical pressure is exerted on plate 6 through shaft [9 and disc 18, holding the plate forward so that probing elements 5 are not bound. When the probing elements 5 contact the charge 22, the resistance to further downward movement is sufficient to depress them into bores T against the weal: pressure of springs 53.

When the downward motion of shaft 2 reaches a predetermined point, disc i8 is automatically retracted, and further downward motion of housing 3 prevented. If the enlarged portions of probing elements 5 are all depressed above plate 6, the pressure from spring blade I6 is sufficient to move the plate 6 rearward so that pin 23 actuates the microswitch 24. If one or more of the pins are not depressed sufiiciently so that the enlarged portion of element 5 is not above plate 6, rearward motion of plate 8 is prevented, and microswitch 24 will not be actuated.

In the embodiment shown, microswitch 24 closes a by-pass circuit which actuates the motive means required to raise shaft 2. As housing 3 rises, spring tensions of springs 65 holds the shell-locking plate I l on the shells, thus permitting withdrawal of the probing elements 5 without danger of a shell rising with the element 5. Continued upward movement of shaft 2 restores the assembly to its original position. As soon as a new cycle is begun, the pressure from shaft I9 and disc ill will return detector plate 6 to its normal position, and elements 5 will again be in the extended position. In the event the assembly is not automatically raised, i. e., if the microswitch 24 is not actuated, the operator will be signaled by conventional means, such as a hell or light, and will then use a separat by-pass circuit to raise the assembly, and recover the rejected block of shells.

A convenient conventional type control and signal circuit is set forth in Figure '7. Referring to the figure, operation of the device is commenced by manually depressing start switch 26. Power is supplied from power source to the stop and start circuit through contact b of the start switch. Relay 28 is thereby actuated and remains actuated through its normally open contact a. Contact 72 of relay 28, on closing, actuates relay 30 through one of either bottom limit switch 25, switch 2% or reset switch 36. Normally open contacts I) and c of relay 3%, upon actuation complete the power supply circuit to the motor 32. The opening of normally closed contact a of relay 30, breaks the circuit to the warning device 33. Contact a of the start switch actuates relay 34 and power is thereby supplied through its single normally open contact to solenoid 35, shifting reverse clutch 36 to its position for raising. The action of the mechanism continues the raising until top limit switch 31 is momentarily opened. Opening of top limit switch 3? closes switch 38 which is ganged to it. In this manner, relay 39 is energized and its sin gle normally open contact is closed. Power is then supplied to solenoid 40, the reverse clutch being thereby shifted to the down position, opening of switch 37 having deactivated relay 34 and solenoid 35. The downward motion can be interrupted by opening of normally closed bottom limit switch 25, thereby cutting ofi power to relay 38. Power is cut on through its contacts b and c and supplied to the warning device through its contact a. In normal operation, however, when all initiator shells are properly loaded, switch 24 is closed momentarily as bottom limit switch 25 opens. Switches 4! and 42 are ganged to switch 24. The closing of switch 24 causes switch 4! to open and switch 42 to close. Power is thereby out from solenoid 4B and supplied to solenoid 35. This reverses the mechanism into its raising cycle. Thus, the reciprocating action of shaft 2 will continue indefinitely unless both switches, 24 and 25, are simultaneously opened. When this occurs the motor is stopped and the warning device is actuated. The operator can raise the device and remove the defective shells by simultaneously depressing start switch 26 and reset switch 3!. The operation can also be stopped through stop switch 29.

It will be apparent that this checking device can readily be utilized in either a completely automatic initiator shell assembly set-up, or as an individually operated inspection station. The full operating cycle requires only a very short period of time, and only simple adjustments are required to adapt the device for use with shells of diiferent sizes or of charges of difierent depths.

The embodiment illustrated is considered failsafe, in that continued operation of the assembly is interrupted if the probing elements are not properly depressed, and thus a block containing a defective shell cannot be accidently overlooked. It would obviously be feasible to have the microswitch control a circuit to a light or a bell to signal the operator, or to automatically remove a block containing a defective shell.

Many variations of the controls devices remotive means to produce the desired sequence of Also, the selection of the motive operation. means for actuation of the shafts 2 and I9 is not a part of the present invention. Since ex- I plosive compositions are present, it may be pref- 3 erab1e to use pneumatic or hydraulic units toreduce the hazard or sparking. The materials usable in the construction of the various parts of the assembly is limited only to those nonreactive to the explosive composition, since there are no moving parts apt to produce sparks in the vicinity of the shells.

In view of the many variations which may be made in the design and operation of the present invention, I intend to be limited only by the following claims.

I claim:

1. A charge checking device for initiator shells comprising a housing having a plurality of vertical bores, an initiator shell positioning area below said housing, a horizontally movable plate within said housing having openings normally in axial alignment with said bores, probing elements projecting below said housing passing through said plate openings and guided by said bores, said probing elements being normally maintained in a downwardly extended position, and having an area of substantially the same diameter as the plate openings at that portion normally at the plate level, and an area of reduced diameter immediately below said portion, means for lowering said housing a predetermined distance towards said shell positioning area, whereby said probes enter initiator shells and contact a charge therein, means exerting a horizontal force on one end of said movable plate, signal means responsive to horizontal motion of said plate, means for raising said housing to the original level, and means for returning said plate to said normal position.

2. A device as claimed in claim 1, wherein the signal means comprises a by-pass circuit actuated by a microswitch.

3. A device as claimed in claim 1, wherein the probing elements are normally maintained in an extended position by compression springs.

CHARLES RUSSELL JOHNSON.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,939,368 Rydmark et a1 Dec. 12, 1933 2,177,821 Dinzl Oct. 31, 1939 2,305,601 Brown et a1. Dec. 22, 1942 

